This application is related to and claims priority from Japanese Patent Applications No. 2002-53512 filed on Feb. 28, 2002, No. 2002-93768 filed on Mar. 29, 2002, No 2002-93769 filed on Mar. 29, 2002, No. 2002-155604 filed on May 29, 2002 and No. 2002-372092 filed on Dec. 24, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a cold-storage type air conditioner for a vehicle including a vehicle engine that is used as a drive source of a compressor. The vehicle engine is stopped when the vehicle stops.
2. Description of Related Art
In recent years, in order to protect the environment and to reduce fuel consumption of a vehicle engine, a vehicle (e.g., economically running vehicle such as a hybrid vehicle) automatically stopping its engine at a time of a stoppage of the vehicle such as in waiting for a change of a traffic signal has been practically used, and hereafter, there is a tendency to increase the number of this-type vehicles. In an air conditioner for a vehicle, a compressor of a refrigerant cycle is generally driven by a vehicle engine. Therefore, in the economically running vehicle described above, the compressor is also stopped at every stoppage of the engine. Accordingly, in this case, a temperature of a cooling evaporator increases, and an air temperature blown into a passenger compartment increases, so that a cooling feeling for a passenger in the passenger compartment is damaged.
To overcome this problem, an air conditioner with a cold storage unit is provided. In this air conditioner, when operation of the vehicle engine (compressor) is stopped and cooling operation of an evaporator is stopped, air to be blown into the passenger compartment is cooled by using cold release operation of the cold storage unit. For example, in a cold-storage type air conditioner disclosed in JP-A-2000-313226, a cold storage tank having therein a cold storage material is disposed in parallel with an evaporator in a refrigerant flow direction, so that refrigerant decompressed by a decompression unit is circulated to the evaporator and the cold storage tank in parallel when the vehicle engine operates. Thus, the cold storage material is cooled while the vehicle engine operates, thereby performing cold storage (cold accumulation) in the cold storage material. When the operation of the compressor is stopped with the stop of the vehicle engine, liquid refrigerant in the cold storage tank is circulated to the evaporator. Accordingly, even when the operation of the compressor is stopped, a cooling capacity of the evaporator can be continuously obtained, so that the passenger compartment can be cooled.
However, in the air conditioner, since the cold storage tank and the evaporator are connected in parallel in the refrigerant flow direction, refrigerant decompressed by a decompression unit such as an expansion valve is divided to be supplied to the cold storage tank and to the evaporator. Therefore, in a large cooling-load condition such as in the summer, an amount of refrigerant circulated to the cooling evaporator becomes deficient, and cooling capacity of the evaporator becomes deficient. Further, after solidification of the cold storage material is completed, that is, after cold accumulation (cold storage) is completed, low-pressure refrigerant generally does not absorb heat from the cold storage material. Therefore, in this case, the low-pressure refrigerant passes through the cold storage tank while almost being not evaporated. Further, the low-pressure refrigerant from the cold storage tank joins with refrigerant at an outlet of the evaporator, and the joined refrigerant is sucked into the compressor.
Because the expansion valve controls a super-heating degree of the joined refrigerant, an opening degree of the expansion valve is also changed in accordance with low-dryness refrigerant from the cold storage tank. Therefore, the open degree of the expansion valve is adjusted excessively smaller with respect to the super-heating degree of refrigerant at the outlet of the evaporator. Thus, a refrigerant flow amount in the evaporator becomes smaller with respect to a cooling load of the evaporator, and cooling capacity of the evaporator cannot be sufficiently obtained. In order to accurately control the opening degree with respect to the cooling load, a solenoid valve is need in a refrigerant passage of the cold storage tank. In a case where the solenoid valve is provided, when the cooling performance is insufficient while the vehicle engine (compressor) operates, refrigerant circulation into the cold storage tank is stopped by closing the solenoid valve. Only when the cooling capacity of the evaporator is sufficient, the low-pressure refrigerant is circulated to the cold storage tank by opening the solenoid valve, and the cold storage of the cold storage material is performed. In this case, because the solenoid valve is required and a control mechanism for controlling the solenoid valve is also required, production cost of the air conditioner with a cold storage unit is increased. Further, the structure of the cold storage unit including the solenoid unit becomes complex, and the size of the cold storage unit is increased. Therefore, the cold storage unit is difficult to be mounted in the vehicle.
In view of the above-described problems, it is an object of the present invention to provide a vehicle air conditioner with a cold-storage heat exchanger, which effectively improves cooling capacity and cold-storage capacity while having a simple structure.
It is another object of the present invention to provide a vehicle air conditioner with a cold-storage heat exchanger, which improves condensation capacity of gas refrigerant in the cold-storage heat exchanger in a cold release mode.
It is -a further another object of the present invention to provide a vehicle air conditioner with a cold-storage heat exchanger, which improves heat-exchanging performance of an evaporator in the cold release mode when a compressor is stopped.
It is a further another object of the present invention to provide an air conditioner with a cold-storage heat exchanger, which can be readily mounted in a vehicle.
According to the present invention, in an air conditioner for a vehicle having an engine that is stopped when the vehicle stops, a compressor is driven by the engine, a high-pressure side heat exchanger is disposed to radiate heat of refrigerant discharged from the compressor, a decompression unit decompresses refrigerant flowing from the high-pressure side heat exchanger, and refrigerant from the decompression unit is evaporated in an evaporator so that air to be blown into a passenger compartment of the vehicle is cooled. Further, the air conditioner includes a cold-storage heat exchanger having therein a cold storage material for performing a cold storage operation where the cold storage material is cooled by refrigerant from the decompression unit, and a cold release operation where refrigerant circulates between the evaporator and the cold-storage heat exchanger so that gas refrigerant evaporated in the evaporator is cooled by cold release of the cold storage material in the cold-storage heat exchanger. In the air conditioner, the cold storage heat exchanger and the evaporator are connected in series in a refrigerant flow, such that the cold storage operation of the cold storage material is performed when the compressor operates, and the cold release operation of the cold storage material is performed when operation of the compressor is stopped with a stop of the engine. Because the cold-storage heat exchanger and the evaporator are disposed in series in the refrigerant flow, refrigerant always flows through the heat-storage heat exchanger and the evaporator by the operation of the compressor when the compressor operates. Therefore, the cooling capacity in the evaporator and the cold-storage capacity in the cold-storage heat exchanger can be effectively improved while the compressor operates. Further, it is possible to improve the cooling capacity and the cold-storage capacity without using a solenoid valve for switching a refrigerant flow in the cold-storage heat exchanger.
Preferably, the decompression unit is an expansion valve that adjust a flow amount of refrigerant in accordance with a super-heating degree of refrigerant at a refrigerant outlet of the evaporator. Further, the cold-storage heat exchanger is disposed upstream from the evaporator in the refrigerant flow. Therefore, a refrigerant flow amount circulating in a refrigerant cycle can be suitably adjusted.
When a tank is disposed downstream from the evaporator in the refrigerant flow such that refrigerant from the evaporator is separated into gas refrigerant and liquid refrigerant in the tank, the tank is coupled to the compressor such that gas refrigerant in the tank is introduced to a suction portion of the compressor. In this case, the cold-storage heat exchanger is disposed downstream from the evaporator in the refrigerant flow so that refrigerant passing through the cold-storage heat exchanger is sucked into the suction portion of the compressor after passing through an inner space of the tank when the compressor operates. Therefore, low-pressure refrigerant passing through the cold-storage heat exchanger is sucked to the compressor after passing through the inner space of the tank, and the liquid refrigerant is stored in the tank. Thus, in this case, even when the expansion valve is not used, it can prevent liquid refrigerant from being introduced to the compressor. Further, because the temperature of refrigerant in a refrigerant passage of the evaporator is decreased from an inlet to an outlet of the evaporator due to pressure loss in the refrigerant passage of the evaporator, the cold storage material can be effectively cooled by the low-pressure refrigerant.
According to the present invention, a tank for storing liquid refrigerant condensed in the cold-storage heat exchanger is provided so that liquid refrigerant is stored in the tank under the cold-storage heat exchanger. In this case, when the operation of the compressor stops with a stop of the engine, liquid refrigerant in the tank is introduced to the evaporator, and gas refrigerant evaporated in the evaporator is introduced to the cold-storage heat exchanger to be cooled and condensed by the cold release operation of the cold storage material. Therefore, when the compressor stops, liquid refrigerant condensed by the cold-storage heat exchanger can be rapidly introduced under the cold-storage heat exchanger by the gravity of the liquid refrigerant. Thus, all the surfaces of the cold-storage heat exchanger can be effectively used for performing heat exchange, and condensation capacity of gas refrigerant in the cold-storage heat exchanger can be improved in the cold release mode. Further, because a tank portion for storing the liquid refrigerant is positioned under the cold-storage heat exchanger, it is unnecessary to arrange the cold-storage heat exchanger at an upper side of the evaporator. Accordingly, the air conditioner with the cold-storage heat exchanger can be readily mounted on the vehicle.
According to the present invention, a pump is disposed to circulate refrigerant between the cold-storage heat exchanger and the evaporator when the operation of the compressor stops, and the pump is disposed such that a flow direction of refrigerant in the evaporator when the operation of the compressor stops is the same as that when the compressor operates. Therefore, even when the cold release mode is performed when the operation of the compressor is stopped, the heat-exchanging performance in the evaporator can be effectively improved. Preferably, the pump is disposed to be exposed in liquid refrigerant in the tank portion. Thus, when the operation of the compressor is stopped, liquid refrigerant can be readily supplied to the evaporator by the operation of the pump.
Preferably, the cold-storage heat exchanger is disposed in the tank, such that refrigerant flowing to an upper space above the cold-storage heat exchanger flows through the cold-storage heat exchanger downwardly from above, and is U-turned in a lower space under the cold-storage heat exchanger to be sucked to the refrigerant suction port. Therefore, even when a part of the cold-storage heat exchanger is positioned in the liquid refrigerant in the tank, heat-transmission performance in the cold-storage heat exchanger can be effectively improved.
When a part of the cold-storage heat exchanger is positioned in the liquid refrigerant of the tank, a partition member for partitioning a space around the refrigerant suction port from the other space in the tank can be disposed. In this case, the partition member has an opening opened at a lower side of the cold-storage heat exchanger. Accordingly, when the compressor operates, refrigerant under the cold-storage heat exchanger can be effectively introduced to the refrigerant suction port from the opening of the partition member.
Preferably, the cold-storage heat exchanger includes a plurality of tubes through which refrigerant from the decompression unit flows, a plurality of fines disposed to be thermal-connected with the tubes, and a shell that is disposed to accommodate the tubes and the fins. Further, the fins are disposed to have plural heat-transmission surfaces contacting the tubes, and the cold storage material is filled in the shell outside the tubes between the heat-transmission surfaces. Therefore, heat-exchanging capacity in the cold-storage heat exchanger can be effectively improved, and the size of the cold-storage heat exchanger can be reduced. Accordingly, mounting performance of the cold-storage heat exchanger can be improved.
Preferably, the tubes are disposed in the shell to extent vertically. Therefore, condensed liquid refrigerant can readily flow through the tubes in the cold-storage heat exchanger. More preferably, the fins are flat plates disposed substantially in parallel by a predetermined pitch, and the predetermined pitch is in a range of 0.5-2.0 mm. In this case, the heat transmission performance of the cold-storage heat exchanger can be more effectively improved.
Further, in the cold-storage heat exchanger, the fins are disposed in the shell to have a predetermined clearance between the fins and the shell. Therefore, the heat-insulation performance of the cold-storage heat exchanger with an outside can be improved, and the cold-storage heat exchanger can be mounted in an engine compartment with a high temperature.